1. Field of the Invention
The present invention relates generally to proper locating of a printhead relative to a print media path in a printer and, more particularly, to a printhead carrier with a height-adjustable bearing mechanism for effecting continuous adjustment of the printhead carrier position to set the proper angle of the printhead relative to a sheet of print media.
2. Description of the Related Art
A conventional inkjet printer includes a frame which defines a print media path along which a sheet of print media is transported through a print zone in the printer. A printhead carrier assembly supported on the frame of the printer includes a printhead carrier adapted to undergo reciprocating movement relative to a carrier frame and across the print media path for carrying and scanning at least one printhead through the print zone. As the printhead traverses the print zone it ejects drops of ink onto the sheet of print media at predefined locations to form a printed image thereon that is expected to be a high-quality replica of image data inputted to the printer for printing. The achievement of a high-quality printed image is dependent, at least in part, on the proper alignment of the printhead carrier relative to the carrier frame to provide the desired gap between the printhead and the sheet of print media. If the printhead carrier is not properly aligned and positioned relative to the carrier frame, the printhead will then not be properly spaced relative to the sheet of print media in the print zone and, as a consequence, the expected high quality of the image printed will be not be attained.
U.S. Pat. Nos. 6,386,681 and 6,692,107, assigned to the same assignee as the present invention, recognize the need to properly align and position the inkjet printhead with the sheet of print media to produce a high-quality replica of the input image data. In the printers disclosed in these patents a printhead carrier is aligned with and supported by a carrier frame in the printer at locations of primary and secondary bearings defined on the carrier. At its primary and secondary bearings, the carrier slidably rides on two guide members of the carrier frame in the form of elongate rods or rails spaced apart from one another. The primary and secondary bearings are formed at locations on the carrier that are preselected for properly aligning the printhead relative to the sheet of print media and also for enabling the carrier to be translated by a suitable translation mechanism bi-directionally along an axis defined by the guide members across the width of the sheet of print media. The translation mechanism may include a belt attached to the carrier and a drive motor coupled to the belt to drive the belt and thereby translate the printhead carrier along the guide members.
More particularly, there are two primary bearings and one secondary bearing defined on the carrier where it rests on the two guide members. The two primary bearings are spaced apart from each other and formed on the carrier adjacent the respective opposite ends thereof. The primary bearings each contact one guide member on a top guiding surface thereof and at two locations thereon. The one secondary bearing is aligned between the two primary bearings, laterally offset both vertically and horizontally from them, and located above them. The secondary bearing is integrally formed by a unitary structure that contacts the other guide member on a top guiding surface thereof and thus at one location thereon.
Other printers are known that employ similar primary and secondary bearings. In many higher-end products, however, the secondary bearing is not integral but actually an additional part fastened onto the carrier. By making the secondary bearing an additional part, the bearing material can be optimized for better wear and a longer life of the carrier. Additionally, in some printers this additional part forming the secondary bearing is made adjustable to change the angular relationship of the printhead carrier to the guide members. However, this additional secondary bearing part has only limited capability in that it can only be used to make a few rough, discrete adjustments which fall short of being able to set the proper angular relationship of the printhead carrier to the guide members.